The FDA Wants to Regulate Them
The FDA regulates some tobacco products, including cigarettes, cigarette tobacco, roll-your-own tobacco and smokeless tobacco. But it wasn't until 2014 that the agency proposed requirements for e-cigarettes, nicotine gels and dissolvable tobacco, among other previously unregulated tobacco products, under the Family Smoking Prevention and Tobacco Control Act. Under these regulations manufacturers are required to disclose all ingredients in their products, and have FDA approval before marketing them. Additionally, e-cigs can't be sold to minors (although the specific age depends on the state in which you live), and all labeling must include health warnings; free samples and vending machine sales are also prohibited [source: Federal Register].
Manufacturers, however, say the e-cigarette is simply recreational, and should not be subject to FDA regulation.